Organic fluorine compound, lubricant, and processing method of magnetic recording medium

ABSTRACT

According to one aspect of the present invention, an organic fluorine compound is represented by a general formula 
       (R-π-E-CH 2 -A-CH 2 -E′) n -π′-G  (1B)
         (where n is an integer of 2 to 5, A is a divalent perfluoropolyether group, π is an arylene group or a single bond, R is an alkenyl group or an alkynyl group, and E and E′ are each independently an ether bond or an ester bond or a group that is represented by a chemical formula       

       —O—CH 2 CH(OH)CH 2 O—
 
     π′ is a group in which n+1 hydrogen atoms are separated from benzene, G is an organic group containing a fullerene skeleton, the n number of groups each of which is represented by a general formula 
       R-π-E-CH 2 -A-CH 2 -E′-
 
     may be the same or different, and at least one π among the n number of π is an arylene group).

TECHNICAL FIELD

The present disclosure relates to an organic fluorine compound, alubricant, and a processing method of a magnetic recording medium.

BACKGROUND ART

Because a perfluoropolyether compound has a large viscosity index, inaddition to being excellent in heat resistance, chemical resistance, andoxidation resistance, a small variation in fluidity (viscosity) over awide temperature range from low temperature to high temperature, anddemonstrates favorable lubricity. Further, a perfluoropolyether compoundhas properties such as being fireproof, not substantially influencing ahigh-molecular material such as rubber or plastic, low vapor pressure,low evaporation loss, low surface tension, and high electric insulation,and is known to demonstrate high performance over an extremely widerange as a lubricant. Thus, a perfluoropolyether compound is widely usedfor various purposes such as lubricating oil such as vacuum pump oil, alubricant for a magnetic disk/tape or the like, a heating medium, and anon-adhesive agent.

As an example of using an organic fluorine compound including aperfluoropolyether group as a lubricant, a disk-like substrate that isused as a magnetic recording medium can be exemplified.

A magnetic recording medium is, in general, obtained by stacking arecording layer and the like on a substrate, thereafter, forming aprotective layer of carbon or the like on the recording layer, andfurther forming a lubricant layer on the protective layer. Theprotective layer has a function to protect information recorded in therecording layer, and to increase sliding of a magnetic head that readsdata.

However, durability of the magnetic recording medium cannot besufficiently obtained only by providing the protective layer on therecording layer.

Thus, in general, a lubricant layer is formed by applying an organicfluorine compound including a perfluoropolyether group on a surface ofthe protective layer as a lubricant. Thereby, durability is enhancedbecause a direct contact between the magnetic head and the protectivelayer can be prevented, and frictional force of the magnetic head thatslides on the magnetic recording medium can be extremely reduced.

As a lubricant that is used for a magnetic recording medium, forexample, an organic fluorine compound that is represented by a chemicalformula

HOCH₂CF₂O(CF₂CF₂O)_(p)(CF₂O)_(q)CF₂CH₂OH  (3)

(where p and q are each an integer of greater than or equal to 1.) isknown. Examples of the organic fluorine compound described above includeFOMBLIN (registered trademark) Zdol (manufactured by Solvay SpecialtyPolymers).

Patent Document 1 discloses a magnetic recording medium in which alubricant as described above is applied on a protective layer.

Further, Patent Document 2 discloses a magnetic recording mediumincluding a lubricant layer made of an organic fluorine compound FOMBLINZtetraol (manufactured by Solvay Specialty Polymers) represented by achemical formula

HOCH₂CH(OH)CH₂OCH₂CF₂O(CF₂CF₂O)_(m)(CF₂O)_(n)CF₂CH₂OCH₂CH(OH)CH₂ OH  (4)

(where m and n are integers, and the average molecular weight of thecompound that is represented by the chemical formula (4) is 500 to5000).

Further, Patent Document 3 discloses a magnetic recording medium inwhich a lubricant solution including an organic fluorine compound thatis represented by the following chemical formula (5) and a solvent isapplied on a protective layer.

Here, p and q are each an integer greater than or equal to 1.

Each of the organic fluorine compounds used in the lubricants of thechemical formulas (3) to (5) contain a straight chain perfluoropolyethergroup, but do not contain an aromatic ring in the molecule.

Also, Patent Document 4 discloses a magnetic recording medium includinga lubricant layer of an organic fluorine compound FOMBLIN AM2001(manufactured by Solvay Specialty Polymers) that is represented by thefollowing chemical formula (6).

Here, p and q are each an integer greater than or equal to 1.

Although organic fluorine compounds that are used in these lubricantscontain, at the ends of a linear perfluoropolyether group, a phenylgroup having a substituent in the molecule, oxygen atoms bonded toadjacent carbon atoms constituting the phenyl group form a ring via amethylene group.

PRIOR ART DOCUMENT

[Patent Document]

[Patent Document 1] Japanese Laid-open Patent Publication No. S62-66417

[Patent Document 2] Japanese Laid-open Patent Publication No. H9-282642

[Patent Document 3] Japanese Laid-open Patent Publication No. 2008-75000

[Patent Document 4] U.S. Pat. No. 5,055,359

SUMMARY OF THE INVENTION Problem to be Solved by the Invention

In order to use an organic fluorine compound including aperfluoropolyether group as a lubricant on a disk-like substrate that isused as a magnetic recording medium, for example, it is necessary toform a lubricant layer on a protective layer and thereafter fix thelubricant on the protective layer so that the lubricant does notdissipate over time.

In order to adsorb a lubricant on a protective layer to form a lubricantlayer, in general, a nitriding process is performed on the protectivelayer.

An organic fluorine compound, which is described in each of PatentDocuments 1 and 2, has a hydroxy group at an end of the molecule, thehydroxy group can form a hydrogen bond with a nitrogen atom provided onthe protective layer. Therefore, the organic fluorine compound adsorbson the protective layer and the lubricant layer is formed.

On the other hand, not performing a nitriding process on a protectivelayer is considered as usable to reduce a production cost, because thenumber of steps is reduced. Further, an increase in polarity can besuppressed due to addition of nitrogen atoms whose electronegativity islarge to the protective layer whose main constituents are carbon atomsand hydrogen atoms in general, polarity increased. Therefore, it isconsidered that there is a merit of enhancing resistance to corrosiondue to humidity in air or the like.

However, in a case where a lubricant as described above is applied on aprotective layer to which a nitriding process is not applied, a hydrogenbond is not formed between the protective layer and the lubricant.Therefore, although a small amount of the lubricant is adhered based ona high viscosity, there is a problem that a lubricant layer having asufficient thickness cannot be formed.

The protective layer is constituted by carbon atoms or diamond-likecarbon (DLC) containing carbon atoms. It is known that a part of thecarbon atoms in the DLC has sp² hybrid orbitals, and the DLC includesdouble bonds similar to bonds of carbon atoms in graphite.

Therefore, it is considered to adsorb a lubricant on a protective layerto which a nitriding process is not applied, by n-n stackinginteractions with an adsorption portion in the lubricant using doublebonds.

Because the organofluorine compounds described in Patent Documents 3 and4 respectively contain, at their ends, a phosphazene ring group and a1,3-benzodioxol group that are ring structures containing alternately asingle bond and a double bond, it is considered that, at first glance,the organofluoric compounds can be adsorbed by n-n stacking interactionson a protective layer to which a nitriding process is not applied.

However, because these ring structures contain non-aromatic rings, theflatness of the ring structures is impaired. Therefore, there is aproblem that, for these lubricants, n-n stacking interactions with aprotective layer to which a nitriding process is not applied areinsufficient, and it is impossible to form a lubricant layer having asufficient thickness.

Therefore, it is considered that by using a lubricant in which ringstructures at the ends are consisting of only aromatic rings and thatcan be assumed to be substantially flat, the lubricant can be adsorbed,by effective n-n stacking interactions, on a protective layer to which anitriding process is not applied.

On the other hand, in a case where a lubricant layer is formed on aprotective layer of a magnetic recording medium, such as a magneticdisk, some lubricant on the protective layer is removed each time themagnetic head flies. As a result, the lubricant layer gradually becomesthinner, ultimately leading to a crash. In order to suppress such aphenomenon, the amount of lubricant fixed to the protective layer isrequired to be higher than a predetermined rate, that is, the bondedratio of the lubricant layer is required to be high.

The bonded ratio of the lubricant layer is a rate of the lubricantremaining after a magnetic disk formed with the lubricant layer isimmersed in a solvent and the lubricant that is not fixed on theprotective layer is washed away.

At this time, there is a problem that it is difficult to obtain asufficient bonded ratio by only n-n stacking interactions that act whena lubricant in which ring structures at the ends are consisting of onlyaromatic rings adsorbs on the protective layer to which a nitridingprocess is not applied.

In view of the above, it is an object in one aspect of the presentinvention to provide an organic fluorine compound so that it is possibleto form a lubricant layer having a sufficient thickness on a protectivelayer to which a nitriding process is not applied and it is possible toincrease the bonded ratio of the lubricant layer.

Means for Solving the Problem

[1] An organic fluorine compound is represented by a general formula

(R-π-E-CH₂-A-CH₂-E′)_(n)-π′-G  (1B)

(where n is an integer of 2 to 5, A is a divalent perfluoropolyethergroup, π is an arylene group or a single bond, R is an alkenyl group oran alkynyl group, and E and E′ are each independently an ether bond oran ester bond or a group that is represented by a chemical formula

—O—CH₂CH(OH)CH₂O—

π′ is a group in which n+1 hydrogen atoms are separated from benzene, Gis an organic group containing a fullerene skeleton, the n number ofgroups each of which is represented by a general formula

R-π-E-CH₂-A-CH₂-E′-

may be the same or different, and at least one π among the n number of πis an arylene group).

[2] The organic fluorine compound according to [1], wherein the A is astraight chain group.

[3] The organic fluorine compound according to [1] or [2], wherein aplurality of the R are the same.

[4] The organic fluorine compound according to any one of [1] to [3],wherein a plurality of the π are the same.

[5] The organic fluorine compound according to any one of [1] to [4],wherein a plurality of the E are the same.

[6] The organic fluorine compound according to any one of [1] to [5],wherein a carbon number of the A is 1 to 100.

[7] The organic fluorine compound according to any one of [1] to [6],wherein the A includes at least one of groups each of which isrepresented by a general formula

—(CF₂)_(x)O—  (2)

(where x is an integer of 1 to 5).

[8] The organic fluorine compound according to [7], wherein the Aincludes 1 to 50 groups each of which is represented by the generalformula (2) in which the x is 1 or 2.

[9] The organic fluorine compound according to any one of [1] to [8],wherein an average formula weight of the A is in a range of 250 to 6000.

[10] The organic fluorine compound according to any one of [1] to [9],wherein the fullerene skeleton of the G is a C₆₀ skeleton, a C₇₀skeleton, a C₇₆ skeleton, a C₇₈ skeleton, or a higher order fullereneskeleton.

[11] The organic fluorine compound according to any one of [1] to [10],wherein the organic fluorine compound is a compound that is representedby the following chemical formula.

[12] A lubricant containing the organic fluorine compound according toany one of [1] to [11].

[13] A processing method of a magnetic recording medium includes:applying the lubricant according to [12] to the magnetic recordingmedium; and irradiating the lubricant applied to the magnetic recordingmedium with ultraviolet light.

Effect of the Invention

According to one aspect of the present invention, it is possible toprovide an organic fluorine compound so that it is possible to form alubricant layer having a sufficient thickness on a protective layer towhich a nitriding process is not applied and it is possible to increasethe bonded ratio of the lubricant layer.

EMBODIMENT FOR CARRYING OUT THE INVENTION

(Organic Fluorine Compound)

An organic fluorine compound according to the present embodiment is acompound that is represented by a general formula

(R-π-E-CH₂-A-CH₂-E′)_(n)-π′-G  (1B)

(where n is an integer of 2 to 5, A is a divalent perfluoropolyethergroup, π is an arylene group or a single bond, R is an alkenyl group oran alkynyl group, and E and E′ are each independently an ether bond oran ester bond or a group that is represented by a chemical formula

—OCH₂CH(OH)CH₂O—

π′ is a group in which n+1 hydrogen atoms are separated from benzene, Gis an organic group containing a fullerene skeleton, and the n number ofgroups each of which is represented by a general formula

R-π-E-CH₂-A-CH₂-E′-

may be the same or different, and at least one π among the n number of πis an arylene group).

In the compound that is represented by the general formula (1B), it ispreferable that every π is an arylene groups due to ease of synthesis.In addition, it is preferable that n is 3 in the compound that isrepresented by the general formula (1B) due to ease of synthesis.

Note that the perfluoropolyether group is a group in which a pluralityof fluorocarbon groups are bonded by an ether bond.

In the following, unless otherwise noted, an organic fluorine compoundaccording to the present embodiment will be described using an organicfluorine compound in which each of a plurality of π is an arylene group.

The organic fluorine compound according to the present embodiment has astructure in the molecule in which a divalent perfluoropolyether groupis bonded via a linking group that is represented by a general formula

-E-CH₂—

with an aryl group in which an alkenyl or an alkynyl group is directlybonded on an aromatic ring

Because the organic fluorine compound according to the presentembodiment contains an aromatic ring that can be considered to besubstantially flat, based on n-n stacking interactions, the organicfluorine compound can be adsorbed on a protective layer to which anitriding process is not applied, and a lubricant layer having asufficient thickness can be formed. Furthermore, because the alkenylgroup or the alkynyl group is attached directly on the aromatic ring,irradiation with ultraviolet light promotes formation of a strong bondbetween sp² hybridized carbon atoms between an unsaturated bondcontained in the alkenyl group or the alkynyl group and the materialconstituting the protective layer (e.g., diamond-like carbon (DLC)). Asa result, the lubricant layer on the protective layer can besufficiently fixed, and the bonded ratio of the lubricant layer can beincreased. Because aromatic rings also contain unsaturated bonds, asimilar effect of increasing the bonded ratio is present, but aromaticrings alone do not have a sufficient effect to increase the bondedratio.

Here, A may be either a straight chain group or a branched chain group,but is preferably a straight chain group. When A is a straight chaingroup, the lubricity and the solubility in a fluorine-based solvent areenhanced.

The carbon number of A is preferably 1 to 100, and is more preferably 5to 40. When the carbon number of A is 1 or more, because the solubilityof the organic fluorine compound in a fluorine-based solvent isenhanced, the organic fluorine compound can be easily applied. Also,when the carbon number of A is 100 or less, because the solubility ofthe organic fluorine compound in a general organic solvent is enhanced,a structural transformation due to an organic reaction of the organicfluorine compound is facilitated.

It is preferable that A includes at least one group represented by ageneral formula

—(CF₂)_(x)O—  (2)

(where x is an integer of 1 to 5).This enhances the solubility of the organic fluorine compound in thefluorine-based solvent, and as a result, it is possible to apply theorganic fluorine compound more uniformly.

It is also more preferable that A contains 1 to 50 groups each of whichis represented by the general formula (2) where x is 1 or 2. Aperfluoropolyether group having such a structure is industriallysynthesized and can be easily obtained, and thus is industrially easy touse.

The average formula weight of A is preferably in the range of 250 to6000, and is more preferably in the range of 280 to 3000. When theaverage formula weight of A is 250 or more, because the solubility ofthe organic fluorine compound in the fluorine-based solvent is enhanced,the organic fluorine compound can be easily applied. Also, when theaverage formula weight of A is 6000 or less, because the solubility ofthe organic fluorine compound in a general organic solvent is enhanced,a structural transformation due to an organic reaction of the organicfluorine compound is facilitated.

It is preferable that R is an alkenyl group having 2 to 4 carbon atomsor an alkynyl group having 2 to 4 carbon atoms.

Specific examples of R include a vinyl group, an allyl group, a3-buten-1-yl group, and a propargyl group. Among these, a vinyl group,an allyl group, or a propargyl group is particularly preferable.

E and E′ are each independently an ether bond or an ester bond or agroup that is represented by a chemical formula

—O—CH₂CH(OH)CH₂O—

but are preferably an ester bond because it is easy to synthesize. Here,although the orientation of the ester bond is not particularly limited,the orientation of a group that is represented by a general formula

R-π-COO—CH₂—

is preferable because it is easy to synthesize.

It is preferable that a plurality of R of the organic fluorine compoundaccording to the present embodiment is the same. Thereby, the number ofsteps required for synthesis can be reduced.

Examples of π include, but are not particularly limited to, a phenylenegroup, a naphthylene group, and the like. Among these, a 1,4-phenylenegroup and a 1,2-naphthylene group are particularly preferable.

It is preferable that a plurality of π of the organic fluorine compoundaccording to the present embodiment is the same. Thereby, the number ofsteps required for synthesis can be reduced.

Examples of π′ include, but are not particularly limited to, a phenylenegroup, a naphthylene group, and the like. Among these, a 2,4,6-phenylenegroup is particularly preferable.

It is preferable that a plurality of E of the organic fluorine compoundaccording to the present embodiment is the same. Thereby, the number ofsteps required for synthesis can be reduced.

G is not particularly limited as long as it includes a fullereneskeleton and can be bonded with π′. Examples of G include a group inwhich a pyrrolidine ring is formed on the fullerene skeleton.

Examples of the fullerene skeleton include a C₆₀ skeleton, a C₇₀skeleton, a C₇₆ skeleton, a C₇₈ skeleton, and a higher-order fullereneskeleton. Among these, a C₆₀ skeleton is preferable.

A C₆₀ skeleton having a higher purity than other fullerene skeletons canbe easily obtained industrially. For this reason, the organofluorinecompound according to the present embodiment can make purity high andcan make lubricity and smoothness favorable.

(Method of Synthesizing of Organic Fluorine Compound)

An organic fluorine compound according to the present embodiment can besynthesized, for example, according to the following synthesis method.

(Compound Represented by General Formula (1B′))

First, a compound that is represented by a general formula

R-π-E-CH₂-A-CH₂—OH  (1B′)

(where A is a divalent perfluoropolyether group, π is an arylene group,R is an alkenyl group or an alkynyl group, and E is a group that isrepresented by a chemical formula

—O—CH₂CH(OH)CH₂O—

or an ether bond or an ester bond) is synthesized.

[In Case where E is Ether Bond]

For example, a compound represented by the general formula (1B′) can besynthesized by cross-coupling an alkoxide, which is generated bydeprotonation of an existing perfluoropolyether compound having hydroxygroups at their ends with a base, with an aryl halide under the presenceof a copper catalyst. This reaction can be carried out, without the useof a solvent, and with heating and stirring as appropriate.

As the base, a generally known ionic base can be used, and examples ofthe base include potassium carbonate, cesium carbonate, potassiumt-butoxide, and the like.

Also, as the copper catalyst, for example, a catalyst generated formedfrom copper (I) iodide and ethyl 2-cyclohexanone carboxylate can beused.

It is preferable that in the aryl halide, an alkenyl group or an alkynylgroup is directly attached on an aromatic ring constituting the arylgroup in advance.

Examples of the aryl halide include aryl iodide, and the like. Amongthese, 4-allyliodobenzene is particularly preferable.

[In Case where E is Ester Bond]

For example, a compound that is represented by the general formula (1B′)can be synthesized by esterification of an existing perfluoropolyethercompound having hydroxy groups at their ends with an acid chloride (forexample, a carboxylic acid chloride) under the presence of a base. Thisreaction can be carried out in a solvent.

Alternatively, an existing perfluoropolyether compound havingchlorinated carbonyl groups at their ends may be esterified with acompound having a hydroxy group as well.

Although the solvent is not particularly limited as long as it candissolve a perfluoropolyether compound as described above, examples ofthe solvent include a chlorine-containing solvent such asdichloromethane and a fluorine-containing solvent such as AK-225(manufactured by Asahi Glass Co., Ltd.).

As the base, generally known inorganic bases and organic bases can beused, and examples of the base include cesium carbonate, triethylamine,diisopropylamine, and the like.

[In Case where E is —O—CH₂CH(OH)CH₂—O—]

For example, a compound that is represented by the general formula (1B′)can be synthesized by a ring-opening addition reaction of an existingperfluoropolyether compound having hydroxy groups at their ends with acompound in which a glycidyloxy group is directly bonded on an aromaticring constituting an aryl group under the presence of a base. Thisreaction can be carried out in a solvent.

Although the solvent is not particularly limited as long as it candissolve a perfluoropolyether compound having a hydroxy group and anionic base, examples of the solvent include alcohol, such as methanoland t-butyl alcohol, a polar solvent, such as N,N-dimethylformamide, andthe like.

As the base, a generally known ionic base can be used, and examples ofthe base include potassium carbonate, cesium carbonate, potassiumt-butoxide, and the like.

(Compound Represented by General Formula (1B″)

A compound that is represented by a general formula (1B″)

R-π-E-CH₂-A-CH₂—OTf  (1B″)

can be synthesized by causing a compound that is represented by thegeneral formula (1B′) to react with trifluoromethanesulfonic anhydride(Tf₂O) to convert the hydroxy group to OTf.

(Compound Represented by General Formula (1B)

Next, a compound that is represented by the general formula (1B) can besynthesized by causing the compound that is represented by the generalformula (1B″) to S_(N)2-react with 2,4,6-trihydroxybenzaldehyde in anaprotic polar solvent such as N,N-dimethylformamide under the presenceof a base and thereafter to react with N-methylglycine and C₅₀fullerene.

[Crude Product]

In each reaction, water or dilute hydrochloric acid is added to thereaction mixture, and as needed, a fluorine-containing solvent such asAK-225 (manufactured by Asahi Glass Co., Ltd.) is added as an extractionsolvent for liquid separation, and the organic layer is dried.Thereafter, by being filtered and concentrated by a rotary evaporator, acrude product is obtained.

[Purification]

The crude product can be used as a lubricant. In a case where higherpurity is required, for example, the crude product can be purified bysilica gel column chromatography or a carbon dioxide supercritical fluidextraction method and then used as a lubricant.

In a case where a carbon dioxide supercritical fluid extraction methodis used, for example, the crude product is placed into a pressurecontainer. Thereafter, while maintaining pressure and temperature in thepressure container, by flowing liquefied carbon dioxide into thepressure container, carbon dioxide is made into the supercritical fluidstate and the crude product is purified by extracting a desiredcompound.

It is preferable that the temperature in the pressure container isgreater than or equal to 31° C. and less than or equal to 80° C. Whenthe temperature in the pressure container is less than 31° C., thecarbon dioxide does not enter a supercritical state. When thetemperature exceeds 80° C., extraction property of the supercriticalcarbon dioxide becomes weak.

Further, it is preferable that the pressure in the pressure container isgreater than or equal to 7.38 MPa and less than or equal to 30 MPa. Whenthe pressure in the pressure container is less than 7.38 MPa, the carbondioxide does not enter a supercritical state. When the pressure in thepressure container exceeds 30 MPa, because pressure resistance propertyof the device is required, the price of the device increases, and as aresult, manufacturing cost increases.

(Lubricant)

A lubricant according to the present embodiment includes the organicfluorine compound according to the present embodiment.

The lubricant according to the present embodiment may be the organicfluorine compound according to the present embodiment or may includeanother organic fluorine compound in addition to the organic fluorinecompound according to the present embodiment.

As another organic fluorine compound, although not particularly limited,for example, an organic fluorine compound that is conventionally knownas a lubricant can be used.

As a commercial product of another organic fluorine compound, forexample, FOMBLIN (registered trademark) series (manufactured by SolvaySpecialty Polymers) and the like may be exemplified.

The content of the organic fluorine compound according to the presentembodiment in the lubricant is preferably greater than or equal to 0.1%by mass, is more preferably greater than or equal to 1% by mass, and isparticularly preferably greater than or equal to 10% mass, in order toactualize more favorable adsorptivity.

The lubricant according to the present embodiment can be, as needed,dissolved in a solvent or dispersed in a dispersion medium to form asolution or a dispersion liquid, and then applied to a surface of amagnetic recording medium, such as a magnetic disk.

The method of applying (a solution or dispersion liquid of) a lubricantis not particularly limited, but for example, a spin-coating method, adipping method, or the like can be used.

In a case where a dipping method is used to apply (a solution ordispersion liquid of) a lubricant to the surface of a magnetic recordingmedium, for example, the magnetic recording medium is immersed in (thesolution or dispersion liquid of) the lubricant placed in an immersiontank of a dipping coating device, and then the magnetic recording mediumis pulled up from the immersion tank at a predetermined speed.

It is preferable that the content of the organic fluorine compoundaccording to the present embodiment in the solution or dispersion liquidof the lubricant is greater than or equal to 0.005% by mass.

Here, as described above, after applying (the solution or dispersionliquid of) the lubricant according to the present embodiment, it ispreferable to perform irradiation with ultraviolet light. Thereby, it ispossible to form a lubricant layer having a sufficient thickness on aprotective layer to which a nitriding process is not applied and it ispossible to increase the bonded ratio of the lubricant layer.

EXAMPLES

The present invention will be specifically described based on examplesin the following. However, the present invention is not limited to thefollowing examples.

(¹H-NMR)

A sample (approximately 10 mg to 30 mg) was dissolved in aCDCl₃/hexafluorobenzene mixed solvent (approximately 0.5 mL) and it wasplaced in an NMR sample tube having a diameter of 5 mm. Thereafter,¹H-NMR spectrum was measured using a Fourier Transform Nuclear MagneticResonance System JNM-EX270 (manufactured by JEOL, Ltd.) at roomtemperature. At this time, to the CDCl₃/hexafluorobenzene mixed solvent,tetramethylsilane was added as a reference material.

Example 1

Organic fluorine compounds according to the present embodiment weresynthesized according to the following synthesis examples.

Synthesis Example 1 Synthesis of Compound 1 (C2) and Compound 2 (C2):[Reaction Formula (7)]

An organic fluorine compound FOMBLIN Zdol whose number average molecularweight (Mn) is approximately 1300 (manufactured by Solvay SpecialtyPolymers) (3.9 g, 3 mmol), copper (I) iodide (72 mg, 0.38 mmol), ethyl2-cyclohexanonecarboxylate (0.12 g, 0.71 mmol), and 4-allyliodobenzene(0.62 g, 2.6 mmol) were mixed, thereafter, while stirring, cesiumcarbonate (3.7 g, 11 mmol) was added and stirring was conducted at 100°C. for 18 hours. Next, the reaction mixture was separated by dilutehydrochloric acid (20 mL) and a fluorine-based solvent AK-225(manufactured by Asahi Glass Co., Ltd) (20 mL), and the aqueous phasewas extracted twice by AK-225 (20 mL). After water washing the organicphase, magnesium sulfate was added and it was dried and filtered. Next,the filtrate was concentrated by a rotary evaporator to obtain a crudeproduct (4.5 g) as an orange brown oily substance.

Next, through purification by silica gel column chromatography(developing solvent:hexane-ethyl acetate (9:1 to 5:1)), a compound 2(C2) was obtained as a colorless oily substance (0.96 g, 0.68 mmol,yield 22%).

Here, p and q are an average degree of polymerization and the order of(CF₂O) and (CF₂CF₂O) in R_(f) ¹ is arbitrary.

It was confirmed by the peaks of ¹H-NMR spectrum that the colorless oilysubstance was the compound 2.

(Compound 2)

Peaks of ¹H-NMR spectrum δ[ppm]: 2.01 (s, 1H), 3.34 (d, 2H), 3.93 (br,2H), 4.31 (br, 2H), 5.02-5.08 (m, 2H), 5.87-6.02 (m, 1H), 6.86 (d, 2H),7.13 (d, 2H)

Synthesis Example 2 Synthesis of Compound 3 (C3): [Reaction Formula (8)]

The compound 2 (0.32 g, 0.23 mmol) obtained in Synthesis Example 1 andpyridine (36 mg, 0.46 mmol) were added to dichloromethane (25 mL).Thereafter, a dichloromethane (5 mL) solution oftrifluoromethanesulfonic anhydride (86 mg, 0.30 mmol) was added dropwiseand stirring was conducted at room temperature for 15 hours. Next, thereaction mixture was washed once with pure water (30 mL) and once with asaturated aqueous sodium carbonate solution (30 mL), and then theorganic phase was filtered. Next, the filtrate was concentrated with arotary evaporator to obtain a compound 3 (C3) (0.35 g, 0.22 mmol, yield96%) as a colorless oily substance.

Here, p and q are an average degree of polymerization and the order of(CF₂O) and (CF₂CF₂O) in R_(f) ¹ is arbitrary.

It was confirmed by the peaks of ¹H-NMR spectrum that the colorless oilysubstance was the compound 3 (C3).

Peaks of ¹H-NMR spectrum δ[ppm]: 3.34 (d, 2H), 4.31 (br, 2H), 4.66 (br,2H), 5.02-5.08 (m, 2H), 5.86-6.02 (m, 1H), 6.86 (d, 2H), 7.13 (d, 2H)

Synthesis Example 3 Synthesis of Compound 4 (C4): [Reaction Formula (9)]

The compound 3 (0.30 g, 0.19 mmol) obtained in Synthesis Example 2 and2,4,6-trihydroxybenzaldehyde (12 mg, 78 μmol) were added toN,N-dimethylformamide (15 mL). Thereafter, cesium carbonate (88 mg, 0.27mmol) was added and stirring was conducted at 70° C. for 16 hours. Next,the reaction mixture was cooled to room temperature, concentrated with arotary evaporator, and then separated using pure water (20 mL) and afluorine-based solvent AK-225 (manufactured by Asahi Glass Co., Ltd) (20mL). Next, the aqueous phase was extracted twice with a fluorine-basedsolvent AK-225 (Asahi Glass Co., Ltd.) (20 mL). After water washing theorganic phase, magnesium sulfate was added and it was dried andfiltered. Next, the filtrate was concentrated by a rotary evaporator toobtain a reddish brown oily crude product (0.35 g). Next, throughpurification by silica gel column chromatography (developingsolvent:hexane-ethyl acetate (9:1)), a compound 4 (C4) was obtained as acolorless oily substance (0.11 g, 25 μmol, yield 39%).

Here, p and q are an average degree of polymerization and the order of(CF₂O) and (CF₂CF₂O) in R_(f) ¹ is arbitrary.

It was confirmed by the peaks of ¹H-NMR spectrum that the colorless oilysubstance was the compound 4 (C4).

Peaks of ¹H-NMR spectrum δ(ppm): 3.34 (d, 6H), 4.28-4.46 (m, 12H),5.00-5.08 (m, 6H), 5.88-6.01 (m, 3H), 6.82-6.91 (m, 6H), 7.17-7.22 (m,6H), 10.34 (s, 1H)

Synthesis Example 4 Synthesis of Compound 5 (C5): [Reaction Formula(10)]

The compound 4 (0.11 g, 25 μmol) obtained in Synthesis Example 4 andN-methylglycine (15 mg, 0.17 mmol) were added tohexafluorotetrachlorobutane (6 mL). Thereafter, a o-dichlorobenzene (12mL) solution of C₆₀ fullerene (11 mg, 15 μmol) was quickly added. Next,after attaching a Dimroth condenser, it was heated in a hot water bathset at 180° C. and refluxed with stirring for 3 hours. Next, thereaction mixture was cooled to room temperature and then concentrated bya rotary evaporator. Next, it was dissolved in an appropriate amount oftetradecafluorohexane and then filtered. Next, the filtrate wasconcentrated with a rotary evaporator to obtain a black oily crudeproduct (0.19 g).

Then, after the crude product was placed in a stainless steel pressurecontainer (20 mm in inner diameter×200 mm in depth) having an inlet andan outlet, while keeping the temperature in the pressure vessel at 60°C., using a supercritical phase chromatography pump PU 2086-CO2(manufactured by JASCO Corporation), supercritical carbon dioxide wasfed to the pressure vessel at a flow rate of 5 mL/min. in terms ofliquefied carbon dioxide. Next, the pressure in the pressure containerwas varied in the range of 9 MPa to 16 MPa, and by-products with threeor more pyrrolidine rings formed on the fullerene skeleton wereextracted and removed. Next, the pressure in the pressure container wasincreased to 24 MPa and the compound 5 (C5) was extracted as 39 mg ofthe black oily material (27% yield). Note that under these conditions, acompound in which one pyrrolidine ring is formed on the fullereneskeleton was not extracted.

Here, p and q are an average degree of polymerization and the order of(CF₂O) and (CF₂CF₂O) in R_(f) ¹ is arbitrary.

It was confirmed by the peaks of ¹H-NMR spectrum that the black oilysubstance was the compound 5.

Peaks of ¹H-NMR spectrum δ(ppm): 2.72 (brs, 6H), 3.31 (brd, 12H), 4.30(br, 12H), 4.44 (br, 12H), 4.99-5.08 (m, 12H), 5.88-6.03 (m, 6H), 6.90(br, 12H), 7.15 (br, 12H)

Example 2

A protective layer made of DLC (Diamond-Like Carbon) was formed on a2.5-inch glass plank for magnetic disk by a high-frequency magnetronsputtering method using carbon as a target in an Ar gas atmosphere, anda simulated disk was made.

Here, the content of nitrogen atoms in the protective layer of eachsimulated disk was measured using a scanning X-ray photoelectronspectrometer (XPS/ESCA) PHI Quantera II™ (manufactured by ULVAC-PHI,Inc.), and only simulated disks, which were guaranteed that the contentof nitrogen atoms in the protective layer was 1 atom %, were used.

Next, as the lubricant, the compound 5 was dissolved in PF-5060(tetradecafluorohexane) (manufactured by the 3M Company) and a lubricantsolution of 0.01% by mass was prepared.

The lubricant solution was then applied onto the protective layer of thesimulated disk using a dipping method. That is, the lubricant solutionwas applied on the protective layer of the simulated disk by immersingthe simulated disk in the lubricant solution placed in the immersiontank of a dipping coating machine and pulling up the simulated disk fromthe immersion tank. Next, after the surface coated with the lubricantsolution was dried, ultraviolet light having wavelengths of 185 nm and254 nm was irradiated for 2 seconds using a low-pressure mercury lampEUV200 US-A2 (manufactured by SEN LIGHTS CORPORATION) to form alubricant layer.

(Average Thickness of Lubricant Layer)

Using a Fourier transform infrared spectrometer Nicolet iS50(manufactured by Thermo Fisher Scientific K.K), by a high sensitivityreflection method, the average thickness of the lubricant layer wasobtained by measuring the intensity of an absorption peak correspondingto a stretching vibration energy of a C—F bond of the infraredabsorption spectrum. Here, thicknesses at four points were measured forthe lubricant layer, and an average value of these was determined as theaverage thickness.

(Bonded Ratio of Lubricant Layer)

The simulated disk, whose average thickness of the lubricant layer hadbeen measured, was immersed in an immersion tank containing Vertrel(registered trademark) XF (1,1,1,2,3,4,4,5,5,5,5,5-decafluoropentane)(manufactured by Dupont-Mitsui Fluorochemicals Co., Ltd.) for 10minutes. Thereafter, the simulated disk was pulled up to wash awaylubricant that was not fixed to the protective layer of the simulateddisk. Then, after the simulated disk was dried, the average thickness ofthe lubricant layer was determined in a manner similar to the above.

The ratio of the average thicknesses of the lubricant layer before andafter the above process was determined as the bonded ratio.

Comparative Example 1

The average thicknesses and the bonded ratio of the lubricant layer wereevaluated similarly to Example 2 with the exception of using an organicfluorine compound FOMBLIN Ztetraol whose number average molecular weight(Mn) is approximately 2000 (manufactured by Solvay Specialty Polymers)(see the chemical formula (4)) instead of the compound 5.

Comparative Example 2

The average thicknesses and the bonded ratio of the lubricant layer wereevaluated similarly to Example 2 with the exception of using, instead ofthe compound 5, a compound 13 (C13) that is represented by the followingchemical formula.

Here, p and q are an average degree of polymerization and the order of(CF₂O) and (CF₂CF₂O) in R_(f) ¹ is arbitrary.

Note that the compound 13 was synthesized using a S_(N)2 reaction froman organic fluorine compound FOMBLIN Zdol whose number average molecularweight (Mn) is approximately 1300 (manufactured by Solvay SpecialtyPolymers) (see the chemical formula (3)) and allyl bromide.

Comparative Example 3

The average thicknesses and the bonded ratio of the lubricant layer wereevaluated similarly to Example 2 with the exception of using, instead ofthe compound 5, a compound 14 (C14) that is represented by the followingchemical formula.

Here, p and q are an average degree of polymerization and the order of(CF₂O) and (CF₂CF₂O) in R_(f) ¹ is arbitrary.

Note that the compound 14 was synthesized using a method similar to thatof the synthesis example 1 from an organic fluorine compound FOMBLINZdol whose number average molecular weight (Mn) is approximately 1300(manufactured by Solvay Specialty Polymers) (see the chemical formula(3)) and iodobenzene.

Table 1 indicates the evaluation result of the average thicknesses ofthe lubricant layers and the bonded ratios.

TABLE 1 AVERAGE THICKNESS OF LUBRICANT LAYER [nm] BEFORE AFTER ORGANICBEING BEING BONDED FLUORINE PRO- PRO- RATIO COMPOUND CESSED CESSED [%]Example 2 COMPOUND 1.23 1.08 88 5 Comparative CHEMICAL 0.47 0.12 26Example 1 FORMULA (4) Comparative COMPOUND 0.34 0.22 65 Example 2 13Comparative COMPOUND 0.75 0.32 43 Example 3 14

From Table 1, it can be seen that the compound 5 used in Example 2 canform a lubricant layer having a sufficient thickness on a protectivelayer that has not been subjected to a nitriding process and canincrease the bonded ratio of the lubricant layer. At this time, it isconsidered that fixing of the lubricant layer is promoted by irradiatinga compound having an alkenyl group or an alkynyl group with ultravioletlight.

In contrast, because the compound that is represented by the chemicalformula (4) and the compound 13 used in Comparative Examples 1 and 2 donot have an aromatic ring in the molecule, a lubricant layer having asufficient thickness cannot be formed on a protective layer to which anitriding process is not applied.

Note that, from the bonded ratios of the lubricant layers of ComparativeExample 1 and Comparative Example 2, it is suggested that fixing of thelubricant layer is promoted by irradiating the compound 13 having anallyl group with ultraviolet light.

In the compound 14 used in Comparative Example 3, the bonded ratio ofthe lubricant layer is a low value because an alkenyl or an alkynylgroup is not directly attached to a phenyl group.

This result shows adsorption of a molecular structure containing an arylgroup, in which an alkenyl group or an alkynyl group is directlyattached on an aromatic ring, included in the compound 5 used in Example2 on a protective layer to which a nitriding process is not applied, andthe effect of fixing of the lubricant layer by irradiation withultraviolet light.

INDUSTRIAL APPLICABILITY

According to an organic fluorine compound according to the presentembodiment, with respect to a substrate having a protective layer towhich a nitriding process is not applied, a lubricant layer having asufficient thickness can be formed by a dipping method, and byirradiating the lubricant layer with ultraviolet light, fixing of thelubricant layer can be promoted, and as a result, the bonded ratio ofthe lubricant layer can be increased.

The present international application is based on and claims priority toJapanese Patent Application No. 2017-128567, filed on Jun. 30, 2017, theentire contents of Japanese Patent Application No. 2017-128567 arehereby incorporated herein by reference.

1. An organic fluorine compound that is represented by a general formula{R-π-E-CH₂-A-CH₂-E′)_(n)-π′}₂-G  (1B) where n is an integer of 2 to 5, Ais a divalent perfluoropolyether group, π is an arylene group or asingle bond, R is an alkenyl group or an alkynyl group, and E and E′ areeach independently an ether bond or an ester bond or a group that isrepresented by a chemical formula—OCH₂CH(OH)CH₂O— π′ is a group in which n+1 hydrogen atoms are separatedfrom benzene, G is an organic group containing a fullerene skeleton, then number of groups each of which is represented by a general formulaR-π-E-CH₂-A-CH₂-E′- may be the same or different, and at least one πamong the n number of π is an arylene group.
 2. The organic fluorinecompound according to claim 1, wherein the A is a straight chain group.3. The organic fluorine compound according to claim 1, wherein aplurality of the R are the same.
 4. The organic fluorine compoundaccording to claim 1, wherein a plurality of the π are the same.
 5. Theorganic fluorine compound according to claim 1, wherein a plurality ofthe E are the same.
 6. The organic fluorine compound according to claim1, wherein a carbon number of the A is 1 to
 100. 7. The organic fluorinecompound according to claim 1, wherein the A includes at least one ofgroups each of which is represented by a general formula—(CF₂)_(x)O—  (2) (where x is an integer of 1 to 5).
 8. The organicfluorine compound according to claim 7, wherein the A includes 1 to 50groups each of which is represented by the general formula (2) in whichthe x is 1 or
 2. 9. The organic fluorine compound according to claim 1,wherein an average formula weight of the A is in a range of 250 to 6000.10. The organic fluorine compound according to claim 1, wherein thefullerene skeleton of the G is a C₆₀ skeleton, a C₇₀ skeleton, a C₇₆skeleton, a C₇₈ skeleton, or a higher order fullerene skeleton.
 11. Theorganic fluorine compound according to claim 1, wherein the organicfluorine compound is a compound that is represented by a chemicalformula


12. A lubricant containing the organic fluorine compound according toclaim
 1. 13. A processing method of a magnetic recording mediumcomprising: applying the lubricant according to claim 12 to the magneticrecording medium; and irradiating the lubricant applied to the magneticrecording medium with ultraviolet light.